Water purification technology is rapidly becoming an essential aspect of modern life as conventional water resources become increasingly scarce, municipal distribution systems for potable water deteriorate with age, and increased water usage depletes wells and reservoirs, causing saline water contamination. Additionally, further contamination of water sources is occurring from a variety of activities, which include, for example, intensive agriculture, gasoline additives, and heavy toxic metals. These issues are leading to increasing and objectionable levels of germs, bacteria, salts, MTBE, chlorates, perchlorates, arsenic, mercury, and even the chemicals used to disinfect potable water, in the water system.
Conventional technologies, such as reverse osmosis (RO), filtration, and chemical treatment are rarely able to handle the diverse range of water contaminants. Additionally, even though they are commercially available, they often require multiple treatment stages or combination of various technologies to achieve acceptable water quality. Less conventional technologies, such as ultraviolet (UV) light irradiation or ozone treatment, can be effective against viruses and bacteria, but seldom remove other contaminants, such as dissolved gases, salts, hydrocarbons, and insoluble solids. Additionally, most distillation technologies, while they may be superior at removing a subset of contaminants are frequently unable to handle all types of contaminants.
Accordingly, sophisticated distillation systems that are continuous, self-cleaning, and recover a major fraction of the input water appear as the best long-term option to resolve increasing water contamination problems and water scarcity. These distillation systems can involve numerous components, including demisters and filters.
Demisters
A demister, which can be part of such a distillation system, is capable of separating heavy particles of steam and lighter particles of steam from a mixed sample. Cyclone demisters operate by forcing contaminated steam into a curved housing, forcing the steam to take on a rotational motion within the curved housing. This rotational motion results in a centrifugal force that forces the heavier droplets of steam to the outer walls of the housing, while the lighter droplets of steam remain relatively closer to the center of the device. Thus, steam that is heavy because it is contaminated with a heavy substance can be separated from steam that is not contaminated with the substance.
To take advantage of this separation of “clean” and “dirty” steam, demisters typically have a downcomer tube in the center of the top of the curved housing, providing an exit pathway for clean steam to leave the housing. Additionally, there is normally a second exit in the demister on the opposite side of the housing from the downcomer tube. It is through this second exit that the dirty steam can leave the demister.
Filter Flow Indicators
Another part that is frequently involved in distillation systems are liquid filtration devices. Examples of such devices include devices that allow only particles of a certain size to pass, filters that remove particulates, filters that remove molecules of particular chemistries, and devices that purify contaminants from water.
Some filter configurations are simple mechanical devices that capture particulates from the water stream and thereby remove such particulates from the water product. Still other devices utilize adsorbents, such as activated carbon, to physically adsorb impurities that are dissolved in the water stream thereby purifying it. Other filter devices are complex systems that use multiple types of filter cartridges and have elaborate electronic control systems to indicate to the user when problems are occurring.
One recurrent problem with many types of filter devices is that the filter unit can become clogged with the matter that is being removed from the liquid. It is often difficult to determine at what point the filter becomes too clogged to function properly. Unfortunately, for many types of filter devices, a clogged filter that is not attended to can break, allowing leakage of the filtered materials into the filtered liquid. Often, this can happen without warning and compromise water quality.
Many types of monitoring systems have been developed to determine the status of a filter unit and to warn the user when the filter is not working effectively. Typical sensor systems include electronic and pressure sensors to indicate when the filter has been clogged and needs either cleaning or replacement. These types of sensor systems can be generally elaborate and expensive.
Product Water Characteristics
The concern for water purity has resulted in the purification aspects and devices described above. Some of these devices assert to eliminate selective impurities that are commonly found in tap water, but that are detrimental to human health. Although water that has been treated so that it is chemically pure will lessen a consumer's water purity concerns, many consumers hold the opinion that the chemically pure water is tasteless and “flat.” Additionally, many consumers desire the presence of certain beneficial minerals in their drinking water.
Spring water is a popular choice for drinking water, as the minerals provide an amount of flavor to the water that chemically purified water does not have. Additionally, spring water contains certain dissolved gasses that also improve the flavor of the water.